Further comment on my May 23, 2003 posting on this subject (see above):
The method I suggested will not give correct theoretical head weights, only approximate, because two ellipsoids which are exactly x units apart along the x, y, & z-axes will not be exactly x units apart at every point on...
See:
http://unicon.netian.com/tank_vol_e.html
Jin Suk Lee maintains this site and includes lots of engineering information. The above URL contains MS WORD downloadable documents containing formulas for fluid volume at arbitrary levels in various horizontal and vertical tanks and some...
I recently published a tank volume article giving rigorous equations for fluid volume in tanks with common type heads. A 2:1 ellipsoidal head would be a typical example. To find the weight of the head, calculate fluid volume using inside and outside dimensions, subtract, mult. by material...
The volume of fluid in a partially-filled spheroid with semiaxes a, b, & c along the x, y, & z axes, respectively, where the fluid height along the z-axis is h (0<=h<=2c), is given by V=(pi)*a*b*h^2*(1-h/(3*c))/c. This formula can be extracted from my tank volume article published in Nov 2002...